This invention relates to the metallization of substrates and more particularly to the measurement and control of metallic films formed on substrates.
In the metallization of substrates, such as foils and the like, a carrier or receptor is placed in a vacuum chamber where metal is evaporated and caused to form a film.
In the general case, the metal being vaporized is located at a specific position within the chamber. As a result, the subsequent vaporization does not produce a uniform film. In partial compensation, the vaporization is made to take place at various positions relative to the substrate. In the case of paper wound on a roll, for example, sources of metal for vaporizationl are distributed at various positions along the axis of the roll, which is unwound and exposed to metallic vapors.
Although the foregoing procedure improves the distribution of metal relative to the carrier, there is a tendency for the deposited film to be nonuniform, particularly in regions between the sources of metal. The latter are commonly known as "boats" because they are shaped like vessels and each contains a pool of vaporizable metal.
Accordingly it is an object of the invention to facilitate the metallization of substrates. A related object is to facilitate the deposit of metallic material on carriers.
A related object is to facilitate the deposit of metallic material, such as aluminum, on paper and plastic sheeting. Another related object is to facilitate the deposit of metallic materials by continuous evaporation in a vacuum.
Still another object of the invention is to control the deposit of metallic material on substrates. A related object is to achieve uniformity in the deposit of metallic films, particularly on substrates such as plastic or paper.
A further object of the invention is to measure the deposit of metallic material. A related object is to measure individual deposits made from different metallization sources. Still another object is to measure metallic deposits with precision, particularly from multiple sources of metallic vapor.
Yet another object of the invention is to control the thickness of a metallic film deposited on a carrier, particularly when produced by multiple vaporization sources.